1. Field of the Invention
This invention relates to the use of certain 1-aryl-3-(4'-alkyl-1'-piperizinyl)-; 1-aryl-3-(4'-morpholinyl)-; and 1-aryl-3-(4'-thiomorpholinyl)-1-propanones in the treatment of Alzheimer's Disease.
2. Description of the Related Art
Alzheimer's Disease is a progressive neurodegenerative disorder affecting 7% of the population over 65 years of age and characterized clinically by progressive loss of intellectual function. This impairment of function is caused by the presence of neuritic plaques in the neocortex and the loss of presynaptic markers of cholinergic neurons. Neuritic plaques are composed of degenerating axons and nerve terminals, often surrounding an amyloid core and usually containing reactive glial elements. Another characteristic pathologic feature of Alzheimer's Disease is the neurofibrillary tangle, which is an intraneuronal mass which corresponds to an accumulation of abnormally phosphorylated tau protein polymerized into fibrillar structures termed paired helical filaments. In addition, the neurofibrillary tangle also contains highly phosphorylated neurofilament proteins. Even the earliest papers on Alzheimer's Disease were clear that both "senile" plaques and neurofibrillary tangles had to be present in abundance to allow a post-mortem diagnosis of the disease. Before any understanding of the molecular nature of these structures was obtained, efforts were being made to understand the relationship between the numbers of these lesions and the progression or severity of the dementia experienced by the patient. The limitations of silver staining were such that early workers in this field were unable to appreciate the complexity of these abnormal structures (Ball, M J, Neurobiol. of Aging, 8: 564-565, 1987). Although early attempts to correlate pathologic lesion counts with clinical symptoms generally yielded poor results, it was clear that the incidence of large numbers of both type lesions were invariably associated with dementia (Perry et al, J. Neural Transmission, 24: 131-136, 1987; Alafuzoff, I., Acta Neuropath, 74: 209-225, 1987; Whitehouse et al, Prog. Clin. Biol. Res., 317: 131-142, 1989; Tomlinson, Neuropathol. Appl. Neurobiol, 15: 491-512, 1989).
More recent work has allowed a clearer definition of the nature of the lesions stained by silver salts. "Senile" plaques are actually two distinct types of structures, the classical plaques described by Alzheimer being composed of degenerating neuronal elements (neurites) surrounding a central core of amyloid, while the other so-called "diffuse" or "primitive" plaque is usually a deposit of amyloid without a halo of degenerating neurites (Tagliavini, , et al, Neurosci. Lett., 93, 191-196, 1988; Dickson, D W, et al, Am. J. Path., 132, 86-101, 1988). These structures are difficult to distinguish from each other with silver stains or with the widely used fluorescent dye, thioflavin S. Early attempts, using silver staining, at correlations between plaque number and extent of dementia, as well as some more recent studies using thioflavin S, were flawed by this inability to define what type of plaque was being counted (Hansen, L A, et al, Neurology, 38, 48-54, 1988; Katzman, R, et al, Ann. Neurol., 23, 138-144, 1988). This becomes very obvious in recent studies, which have consistently reported that amyloid plaques can be found in large numbers in the brains of the majority of the very elderly (over 80 years), and are only rarely associated with dementia when present without evidence of degenerating neurites (Davies, L, et al, Neurology, 38, 1688-1693, 1988; Delaere, P, et al, Neurosci. Lett., 116, 87-93, 1990; Dickson, D W, et al, Neurobiol. Aging, 13, 179-189, 1991).
The counting of neurofibrillary tangles also fails to give an accurate picture of the extent of neurofibrillary degeneration. Again, the presence of large numbers of tangles is invariably associated with a profound dementia, and some index of disease severity can be gained from tangle counts (Tomlinson, B E, Neuropathol. Appl. Neurobiol., 15, 491-512, 1989; Delaere, P, et al, Acta Neuropath., 77, 645-653, 1989). Electron microscopy first revealed that tangles were composed of masses of paired helical filaments (PHF) filling the cytoplasm of neurons (Terry, R D, et al, pages 145-155, In CIBA Foundation Symposium on Alzheimer's Disease and Related Conditions. Ed. by Wolstenholme, G E W, O'Conner, M, J and A Churchill, London, 1970). These studies also clearly showed that degenerating neurites also contained PHF, a fact only widely appreciated much later, when the use of antibodies to PHF became common (Wolozin, B L, et al, Science, 232, 648-650, 1986). Thus, both the plaques and the tangles of Alzheimer's Disease contain PHF. The use of antibodies to PHF also revealed the widespread presence of these paired helical filaments in neuronal processes (Brun, A, Prog. Clin. Biol. Res., 317, 285-293, 1989). Thus, the presence of PHF is much more widespread than was first suspected, and is today considered to be an indication of a widespread neuronal disease, of which the neuritic plaque and the neurofibrillary tangle are only the most obvious signs (McKee, A C, et al, Ann. Neurol., 30, 156-165, 1991). It has been estimated that as much as 90% of the PHF in the cortex of the average Alzheimer case is present in neuronal processes rather than in the plaque or tangle (Wolozin, B L, Ann. Neurol., 22, 521-526, 1987). Much of the early and indeed the present confusion with regard to diagnosis and severity of Alzheimer's Disease comes from the failure to appreciate the complexity of the pathology in this disease, although the occurrence of significant amounts of PHF in the brain is always associated with severe dementia (Hyman, B T, Current Opinions in Neurology and Neurosurgery, 5, 88-93, 1992). These results suggest that good correlations can be obtained between the concentration of PHF proteins (sometimes referred to as Alzheimer's Disease Associated Proteins or ADAP) in the cerebral cortex and the degree of dementia measured prior to the death of the patient (Ghanbari, H A, et al, JAMA, 263, 2907-2910, 1990).
It is noted that the terminology used to describe the abnormal protein complexes composing the fibrillar pathology in Alzheimer's Disease can be confusing. PHF is a morphological designation, describing abnormal filaments found in neurofibrillary tangles. An abnormal protein species migrating at 68 kDa, electrophoretically, and observed on immunoblots of tissue from AD brains was termed A68 (Wolozin, B, et al, Science, 232, 648-650, 1986). A protein complex shown to be specific for AD by immunochemical analyses was designated Alzheimer's Disease Associated Protein or by the acronym, ADAP (Ghanbari, H A, et al, JAMA, 263, 2907-2910, 1990). It is now known that A68 and ADAP, when viewed by the electron microscope, are PHFs. These PHFs have been further shown to contain, primarily, the microtubule-associated protein, tau. Hence, the terms A68, ADAP, PHF and PHF-tau are often used interchangeably. Thus, they are meant to be interchangable herein.
A series of important studies have suggested that the progression of Alzheimer's Disease can be defined pathologically by careful neuroanatomic studies of large numbers of brains from elderly humans, (Braak, H, et al, Neurosci. Lett., 103, 24-28, 1989; Braak, H, et al, Neuropath. and Applied Neurobiol., 15, 13-26, 1989; Braak, H, et al, Acta Neuropath., 82, 239-259, 1991; Braak, H, et al, European Neurology, 33, 403-408, 1993). The Braak's focus is almost entirely on the development of neurofibrillary pathology, which begins in the entorhinal cortex perhaps years before the clinical signs of the disease are apparent. The progression of Alzheimer's Disease is thought to be somewhat unusual, in the sense that the disease progresses by the involvement of more and more neurons in the formation of PHF, in an anatomic sequence which is to some extent predictable. In the initial stages, only those neurons of the entorhinal cortex contain PHF, in later stages, neurons of the CA1 and CA2 pyramidal layer of the hippocampus contain these structures, and still later, neurons of the association cortex begin to show evidence of PHF formation. Clearly, prevention of PHF formation even after the process is underway in the hippocampus could limit the disease to this brain region, at which point clinical problems are confined to some loss of short term memory. Patients first seek help at a stage when PHF pathology is largely limited to the hippocampus (Berg, L, et al, pages 9-25, in Alzheimer's Disease, Eds., Terry, R D; Katzman, R; Bick, K L. Raven Press, N.Y., 1994). To prevent the progression of Alzheimer's Disease at this point would clearly be a major benefit to the patient (Davies, P, pages 327-334, in Alzheimer's Disease, Eds., Terry, R D; Katzman, R; Bick, K L. Raven Press, N.Y., 1994; Khachaturian Z S, et al, pages 445-454, in Alzheimer's Disease, Eds., Terry, R D; Katzman, R; Bick, K L. Raven Press, N.Y., 1994).
Attempts to determine the molecular nature of the PHF were hampered at first by an approach which attempted to purify PHF from isolated neurofibrillary tangles. Once incorporated into the macromolecular complex that is the tangle, PHFs become extremely difficult to solubilize for protein analysis. The microtubule-associated protein tau appears to be a major antigenic component of PHF. The repeat region of microtubule-associated protein tau forms part of the core of the paired helical filament of Alzheimer's Disease (Goedert, M, et al, Proc. Nat'l. Acad. Sci., 85, 4051-4055, 1988; Wischik, C M, et al, Proc. Nat'l. Acad. Sci., 85, 4506-4510, 1988).
The involvement of protein phosphorylation in the formation of PHF has been suggested by a variety of studies which have shown that tau in PHF is hyperphosphorylated (Kosik, K S, et al, Ann. Med., 21, 109-112, 1989; Goedert, M, Trends in Neurosciences, 16, 460-465, 1993; Iqbal, K, et al, Act Neurobiologiae Experimentalis, 53, 325-335, 1993). There is suggestive evidence that several other proteins, especially neurofilaments and other microtubule associated proteins (MAPs) are also hyperphosphorylated in the brains of patients with Alzheimer's Disease (Lovestone, S, et al, Current Opinions in Neurology and Neurosurgery, 5, 883-888, 1992).
In 1985, a monoclonal antibody ALZ50 was raised (produced by hybridoma cell line ATCC No. HB9205) that recognized a 68 kDa polypeptide (termed A68) in immunoblots of the vulnerable brain regions in AD, but not in control brains, (Wolozin, B, et al, Science, 232, 648-650, 1986). Immunohistochemical analysis with this antibody indicated an intense reaction with neurofibrillary tangles and, in later experiments, with the PHF's, as well. The discovery of A68 was the first report of a biochemically determined abnormal protein species associated with the fibrillar pathology in AD.
In other laboratories in 1986, monoclonal and polyclonal antibodies recognizing the microtubule-associated protein, tau, were shown to react with neurofibrillary tangles, and subsequently, with PHFs (Grundke-Iqbal, I, et al, Proc. Nat'l,. Acad. Sci., 83, 4913-4917, 1986; Kosik, K S, et al, Proc. Nat'l. Acad. Sci., 83, 4044-4048, 1986). Furthermore, biochemical analyses of the protease-resistant "core" of the PHF demonstrated the presence of peptides containing the tau sequence, (Goedert, M, et al, Proc. Nat'l. Acad. Sci., 85, 4051-4055, 1988; Wischik, C M, et al, Proc. Nat'l. Acad. Sci., 85, 4506-4510, 1988). Additionally, monoclonal antibodies, whose epitopes spanned the tau molecule, all were shown to react with neurofibrillary tangles in AD brain (Kosik, K S, et al, Neuron, 1, 817-825, 1988). Much later, it was determined that the ALZ50 antibody reacts with the extreme amino terminus of the tau molecule, (Goedert, M, et al, Neuroscience Letters, 126, 149-154, 1991).
In 1990, in an attempt to purify A68, a more readily soluble preparation of PHFs was isolated (Greenberg, S and Davies, P, Proc. Nat'l. Acad. Sci., 87, 5827-5831, 1990). Immunoblots of these structures indicated that three closely migrating electrophoretic species, the slowest migrating of which was ca. 68 kDa in size, all reacted with ALZ50 and tau antibodies (Lee, V, et al, Science, 251, 675-678, 1991). This indicated that the A68 complex of proteins is, to a large extent, composed of the tau protein. This polymerized form of tau was shown over the years to be in a hyperphosphorylated state.
Other monoclonal antibodies raised against human PHF preparations are the antibodies PHF-1 and TG3. While these antibodies display robust affinity for paired helical filament preparations, they only have trace reactivity towards normal adult tau. Further studies revealed that the monoclonal antibody PHF-1 has a reduced affinity for PHF which has been treated with alkaline phosphatase or hydrofluoric acid, thereby suggesting that this antibody recognized a phosphorylated epitope(s) in paired helical filaments. These phosphorylated epitopes (recognized by PHF-1) reside within the C-terminal fragment of the tau protein, at serine 396 and 404 (Trojanowski, J. Q., et al, Clin. Neurosci., 1, 184-191, 1993). The epitope(s) recognized by TG3 has not been mapped yet.
To date, it has not been possible to consistently induce the formation of Alzheimer-like epitopes either in vivo or in vitro. Hence, there is a need for an assay for the determination of tau protein, paired helical filaments and mechanisms involved with Alzheimer's Disease. There is further a need for an assay suitable for screening for drugs which may prevent or decrease Alzheimer's Disease activity.